There is a new family at the chapel I attend.  From what I understand, they have been married about 15 years, and have four children.  They both appear to be about 40 years old.  They've only been attending our chapel for a month or so, so I haven't had a chance to get to know them very well, but they appear to been good Catholics.  I have no reason to believe otherwise.

However, some long-standing members of the chapel have voiced concerns about these newcomers, saying that if they have been married for 15 years and following the Church's teachings, they should have more than four children.  To me, this kind of talk is beyond the pale; lay people in the pews have no business policing the number of children other people have, particularly when they have no real evidence they are committing any kind of sin.  These pew-police (many of whom are unmarried, by the way), to me, seem to have a very unhealthy obsession with the number of children other people have, and want nothing more than to find fault in other's behavior.  I'm worried this behavior may drive this poor family away from the chapel.  What should I so, if anything?  Has anyone else encountered this type of thing?

Whenever the opportunity arises make them feel welcome.
There could be many reasons for their having 4 children
NONE OF WHICH ARE ANYBODY'S BUSINESS.
If the busybodies voice anything about it in your presence, I
hope you will let them know charitably that they have no
authority to judge.
If it happens again you might not have to be so charitable.
We are called to instruct the ignorant (perhaps also the rude
and malicious).