Going to start this out by saying that I understand that wedding gifts are appreciated, not expected and help from family is appreciated, but not expected. But this is a pretty odd coincidence.
To set the stage, we are both extremely close to our own/each other's families. My mom, who is an amazing single mom and is not well off by any means graciously paid for about 25% of our wedding. His parents graciously paid for about 10% plus the rehearsal dinner. I should mention that they are pretty comfortable and his mom is unfortunately extremely controlling. His siblings (aged 28-37) were members of the bridal party, his nieces were flower girls, and I made sure to include his family in decisions for every aspect of planning.
We finished opening gifts and received such beautiful cards, well wishes, and generous gifts from every single person that attended except for his parents (which was expected due to their contribution) and his siblings/spouses and all of their family friends - 10 adults and 4 kids in total.
Personally, I couldn't imagine showing up to a wedding empty handed, especially for a sibling. So we're thinking one of two things happened: his mom collected all of their cards and either forgot to drop them into the box or gave them to the wrong person and they were taken, or she told everyone on her side not to give us a card or anything because they helped us pay for it.
We don't want to sound ungrateful, but we're also just so perplexed by the situation. Should we say anything? What should we say?