Yes, it's possible they were younger cousins. It's also possible that they were grand-nephews rather than nephews. It's also possible that they weren't actual nephews but were the husbands of nieces, who were writing on behalf of their wives (as was seen as proper in some circles). I've seen both those situations in my own family.

All the best,
Miriam BULWAR DAVID-HAY,
Raanana, Israel.