My eldest DS is 26, he's been with his partner for 2.5 years, they live together, she is lovely. I see DS about twice a year, call about once a month and we have a family group chat active most days.
2 weeks ago DS and his gf went to Portugal (where she is from) on holiday, they sent loads of pics in the group chat.
Today while I was doing the shopping I ran into the mum of DS's childhood best friend, we chatted and she said "you must be over the moon at the news" I had no idea what she was talking about which was very embarrassing and then she told me that her DS had mentioned my DS and his partner were engaged.
I've messaged DS about it now, but no reply (only messaged an hour ago and I know they are meeting up with friends and going to a gig tonight). DH also didn't know, nor did DS2 or DD.
AIBU to be really hurt and confused by this? He never uses his social media and his partner doesn't have any of our family on hers, so there was no way for us to have found out incidentally.