your boyfriend has basically abandoned his child. he doesn't get to have hurt feelings that the little boy thinks grandpa is daddy - he's the reason for that.

further, it's not mom's job to 'correct' her son that grandpa isn't daddy, if daddy is generally nowhere to be found. if daddy was around, that correction wouldn't need to be made. see what i'm saying here? likewise, it's not mom's family's job to foster a relationship between father and son. it's DAD's job to do that, a job he is abdicating.

he also doesn't get to be 'crushed' when this happens, or when he sees his son and notices his developmental delays. after all, the kid's mom and grandparents have to face that EVERY DAY, while your boyfriend gets to hide off in a corner with you and whine that his son doesn't know who he is.

you're asking the wrong question here. the question isn't, "should i talk to my boyfriend about his son?" the question is, "do i want to be in a relationship with someone who would abandon his child, for all intents and purposes, because it's 'inconvenient' and/or uncomfortable?"

i'm taking a bit of a hard line here because you're basically telling my story and my son's story (replete with developmental delays), only in ours, 'dad' was your boyfriend.

if you want to have a talk with your boyfriend about his responsibility here, by all means do so. yes, you have the right to. hopefully it will make a difference. if it doesn't, though, you should probably think two or three times about whether this is a guy you want to proceed with, because i can assure you, he's not unlikely to treat his parental responsibility any differently when it's a new baby mama.