Both SO and I come from divorced families. My mother has remarried, as has his father. The other two parents are single.

At the beginning of my pregnancy, my mother started referring to her husband as a "Grandpa."

Mom's husband and I have not had the best relationship - he treated her poorly when I was in high school. They divorced once and then remarried a few years later. Our relationship has gotten better though and I respect him for making my mom happy now.

I know it would upset my father (who I love dearly) if my son were to call Mom's husband Grandpa. He's been looking forward to the day he can be Grandpa and I don't want to deprive him of that. I told mom something along those lines, and said we'll have to come up with another name for her husband.

As far as my in-laws: My father in law married a woman my age. I understand that MIL doesnt mind sharing "Abuela (Grandma)", I don't think my 30 year old step mother in law wants to be referred to as Grandma.

I know eventually my child will come up with names for them eventually, but I will have to refer to them as something when I talk to my child.

So:

Any suggestions on names for:

Mothers Husband (Older American but don't want to disrespect my dad)
FIL's Wife (30 year old Peruvian)

It feels awkward and tricky and I don't want it to be, but dont want to call them by their first names either.