Hmmm...I'm a fairly new boy mommy (6.5 months) so I never have thought about that. I don't have a whole lot of contact with my mil, but she's close to dh's sister and sil bf'd her 3 kids so I know that mil's at least conscious of how it works in today's society (sil bf'd in front of us all) but mil was verrrrrrrrrrrrrrry ecstatic to have the opportunity to bottlefeed ebm to ds, so there's always that.
Not the same, but I remember my dad gingerly asking me if I was going to BF...and his sense of relief when I said yes. He didn't want to offend or upset me if I said no, but once I said that I was, he was all "oh good. It really gives them the best start in life." My DH was pretty adamant that I give ds the best nutrition possible, and even though I was already planning on bfing, his enthusiasm for it certainly helps keep me going.
I was still pregnant when the Notes from the Underground episode of when the husband was promoting bf, saying that he was smarter and had thicker hair, etc, having been bf'd---and then he learned that his mother hadn't bf'd him and instantly he grew all insecure and fretted over not being musically talented, why he wasn't good at sports, etc. I was just kinda sitting on the couch watching but my dh was rofling about it. The twist was, the character was wetnursed by a neighbor, but I was always so impressed how that little storyline tickled and spoke to my DH.

Your boys can be lactivists too!