To preface this, I think my PiL are quite nice people. I don't know them very well, I've probably met them less than 10 times in the 6 years I've lived with DH but generally they seem like pleasant, friendly people. They live 2 hours drive away.
Since DS was born 2 years ago I've felt a bit resentful of them. They visited when he was born and we visted them (my suggestion) when he was a few months old. They haven't seen him again until last week. MiL would occasionally ask how DS was via fb message but really they all seemed disinterested.
I felt hurt (?) that they weren't interested in DS and a bit sad for DS that he wouldn't have a good relationship with them.
Since last week's visit MiL has become enamoured with DS, she now wants to visit again this week and has been posting pictures of DS on her Facebook and enjoying being complimented by people on her gorgeous grandson.
I should be really pleased.
I'm actually really irritated. He's MINE. He's my gorgeous DS. Who she's mostly ignored for 2 years and now she's busy showing him off like she has something to do with him. 
I want DS to have a good relationship with his grandparents and I know that my sudden possessiveness is unreasonable but I can't stop quietly seething about it.
He's not even my pfb!