MIL & FIL are grandma & papa (same as with their other grandkids)
my mum is nanna (because she couldnt make up her mind & thats what stuck) & her partner is Da (he isnt related to our kids but we wanted him to have something)
My father is nothing, he doesnt make an effort, has only seen DD twice & I dont think he even knows about DS, so he isnt known as anything