I am INCREDIBLY long-winded, it turns out, and very disjointed. It might be best to skip my reply b/c it might not make any sense besides "you're not alone". I think that maybe I'm going through some sort of something, b/c every other post is about my MIL, LOL.
You've been warned.
I'm glad to know there are more. I cant' really say if DS is the least or most favorite with my MIL, it's confusing!
I think I can say he was FIL's favorite, but FIL died 7 months ago.

The *one* good thing we can say (in private...we say good things in front of DS) about FIL is that he was a terrific grandpa.
But my MIL...it's odd. She had two granddaughter's even before DH and I got married. The eldest is a very lovely, dainty girl, very well behaved. The second girl is more tomboyish, she is more burly compared to her older sister. Their personalities and physical presence is obviously different. BUT they were both treated well by MIL.
Then DS arrived. MIL is from a culture that values boys any day of the week over girls. So you can SEE her wanting to treat DS better. But...DS isn't a well-behaved, princessy girl (even the second granddaughter has become that way over the years). He runs and jumps and yells. And hugs and kisses and squeezes gently. He also looks MUCH different. DH and his sister are half-Korean. DH's sister's first husband is caucasian like me. His and SIL's daughters actually look MORE Korean than their mom or my husband, even though they are less. Actually, the second girl's hair is curly and lighter than her sister's, whcih was another difference...the oldest has straight black hair that falls perfectly...
Meanwhile we say that my Irish and DS's 1/4 Welsh got together and had a Celtic party, and DS arrived with Ronald McDonald shocking orange hair...it's settled down into copper/red, and he has amber eyes (his eyes match his hair but you cant' say he has RED eyes even though they are the same color).
So that's another confusing aspect to their relationship, with different "looks" and underlying questions of paternity...though I think everyone who spends time with DS can see that he is the spitting image of both MIL and DH when they were children...all you have to do is put the pictures in black and white, and you can see the likenesses.
But you know, my husband was the "bad" child. The oldest boy, well you can't get rid of the oldest boy, because he's the one that will take care of the parents. He's 9 years older than DH, and was a little adult, taking care of DH and later SIL when my MIL couldn't/wouldn't. So oldest son is perfect (despite the 5 years of the parents not speaking to him because he had the utter gall

to be gay (he would have kept it secret from them forever, but a boyfriend who quickly became an ex outed him to my FIL)). My SIL was the girl, and she was perfect in FIL's eyes. MIl and SIL had typical mom/daughter issues, and they HATED her husband (he deserved the hate, was an ex-con --bank robber and that limits your future hireability -- that met SIL while she was a counselor in his half-way house, he is an active heroin user, and SIL would say they broke up, get 1000s of dollars from her parents, then they'd get back together).
But DH, well, he was the liar. He never did lie, until his father REFUSED to believe him about something incredibly trivial. Finally DH lied and said that he DID do it, DH was punished heavily, and from then on he was the son who lies. When I first met MIL, after the trial of fire she created emotionally and verbally that I endured while trying to figure out my first Korean meal EVER (nothing was familiar, I had to ask DH about every single thing but the rice), she went through DH's faults, including lying. He could do no right. He gave his sister a car he owned, because his parents made him b/c she coudln't afford a car. She then drove it into the GROUND (she destroys cars like no one but a demolition derby driver does). And needed another car. She has been given more cars that DH can count, and each one of them is destroyed. Before FIL went into the hospital, he GAVE her a car outright...without changing the title. Do you know what a pain it is to have a title changed when the owner of record has died? Even in a community property state? And when the new owner ALREADY has a parking ticket on it? DH moved back in with his mom after she had two heart attacks (which is why he was a 28 year old living with his mommy when I met him), to take care of her. The other kids ran away from the situation.
And when FIL died, it was DH by his side, and before that it was me calling the hospital every night to get the information (they never had the Korean interpreter there for MIL, and the nurses talked SO fast, and MIL lets pride get in the way of saying "I don't understand"). And for two months DH, DS, and I gave up every aspect of our life to nearly live with her, helping her get on her feet, I got her pension and SS benefits switched over so that the very next check was the correct check and she didn't have to go a month without money...we got things switched over, we slept overnight in her incense-filled apartment (she's Korean-Buddhist and traditional in her mourning and praying, and burned something like 20 sticks at a time, and I'm allergic) that otherwise makes me ill b/c she uses mothballs in everything...
We were the good ones who did EVERYTHING for her during that time. Then SIL comes over to share a bucket of KFC with her (we're vegetarian), and 2 months of avoidance is *POOF* forgiven. And BIL decides to buy (give her money for payments, and once it's paid off he'll take it) a vehicle she couldn't get rid of (some weird bankruptcy loan on an RV that she can only pay OR have repossessed...no refinancing, no selling, nothing but those two options), and those 2 months are forgiven as well.
But after 2 months of taking care of her, the day I had a 90 minute conversation with the IRS for her (wherein I found out very very bad news about the state of her taxes since '01); while I'm still in tears about what FIL did and how bad it's going to get for MIL (I was also the one who found out that FIL had forged her name and had BIL's former partner "witness" it to steal 20K from her life insurance 6 months before he went into hospital), while I'm trying to figure out what we can do for her...she decided to lay into me about not calling her to "say 'hi'", like her sisters' daughters in law do for their mothers in law....
And *poof*, just like that, I was done with her.
I do still encourage DH and DS to visit her, but I'm conveniently busy. I invited her and her visiting sister and sister's husband to DS's birthday party, and she brought him 4T clothes bought too long ago to exchange...DS just turned 3 and is not incredibly tall or hefty (he's tall, and he's heavy, but he's trim and strong, and JUST now is growing out of 2Ts and she KNOWS this). Great, now he has two outfits for next year, but that doesn't help him THIS year.
Meanwhile, when I was going to her house, I saw the cousins princess coloring books, the barbie stuff, overnight things, all over the place...
