My dad did the same. 14 yr ago, my mom died at in her early 60s from pancreatic cancer. 3 months after that, he started dating 1 of her good friends on the sly. He lied about it a lot at first, got mad at us when he got caught. The woman was still married at the time. He even tried to add her as a domestic partner to his health benefits at work at the time. He then asked her to marry him, she accepted, then he wouldn't tell my sister or I what the wedding date was. We found out after the fact that they got married on the 1 yr anniversary of my mom's death.
In the year and a half after my mom died, he also got rid of literally all of our family mementos and photos, shipped all of it to my house. He basically erased all the memories of our family from his house.
Since my mom died, my dad is a different person. He's not a nice guy. Is also self-absorbed, bitter, passive-aggressive, and manipulative. His wife is also not a nice person. I don't understand why my mom was friends with her.
Couple of pieces of advice to consider, given your situation w/your own dad:
- don't expect him to behave any better. Don't expect it to improve.
- Figure out what your own personal boundaries are. Be prepared to enforce them with your dad.
- when you enforce your boundaries with your dad, expect him to get mad and possibly have a tantrum about it.
- when he gets mad and has a tantrum, put him in a time out for whatever amount of time you feel is necessary.
- grandparenting is a privilege, not a right. He shouldn't be allowed to behave poorly in front of your children (if you have children).
- You are an adult just like he is. And you have a right to decide what behavior you are and are not willing to put up with.
- Just because you ask him to stop lying to you doesn't mean he actually WILL stop lying. Expect that it actually might increase and he'll just get better at covering up his lies.
- Don't cave to pressure from other extended family members who might try to pressure you into just putting up with his nonsense because he's your dad.
Feel free to PM me if you want to chat further.