So bit of back story, I have 2 dds, after my second I had a bit of time of it. It was touch and go for me, dd was fine. But after she was born I was full of the joys of being alive and having more children wasnt even on my radar.
I had 2 names that I liked for boys and just a few weeks after my traumatic time DSIL came to visit telling us she was pregnant, great news, and that if it was a boy she was planning on using my 2nd boys name choice as "you'll obviously not need it now" 
So dn has a lovely name.
Fast forward 5 years and I'm still in my early 30s and DH and I have said that we will give it 2 years until I finish a course I'm doing and maybe consider a 3rd.
However, my other DSIL is pregnant and informed us yesterday if she has a boy she's using our 1st choice...
They are not common names, not even in the top 100. Her DH doesn't like the name.
So, I know it's not definite we'll have a 3rd and if we do it will probably be another girl but am I being unreasonable to say "that's great it's a lovely name, in fact, if we ever have a boy we'll still be using it"??
I'm actually really hurt by it, I know it's ridiculous. She might have a girl so it might be a non issue.
Both DSIL had girls first and had their own choice of boys names, so unsure why they both changed to "my" names when it came to the second children.