for the child
1. social-POV : to have a siblings > only child (IMO, just me)

for. adult
1. u felt unfair for the blackmailing part: really have to let ur wife know about how u feel
2. and try to understand why the wife wants it. real reason behind

since u mention this topic started since the relocation thing involved
anyhow i dont want to advise anything to TS. none of my business

to me:
1. i would want my kid to have siblings
2. and i just want to know if both (wife/husband) wants the same.

to raise a child needs commitments from both of u guys. (not saying single parents cant do so)
but since u guys are still married then it has to be a joined-effort

to avoid issues like: 'u want kids, u take care'