In NICU we only allowed grandparents - most of the aunts and uncles had young kids of their own, and our twins came in November - height of cold and flu and RSV!
Once home we didn't allow visitors, and with family, we didn't allow kids 10 and under. Handwashing was a must, and if anyone was coughing or sniffling, they weren't allowed to hold the babies.
We tried to be gentle about communicating the rules, and explained how dangerous RSV is, yet we did meet with a good bit of resistance from family. My MIL's sister was the worst, she kept wanting to kiss the babies on the lips, and I would ask her not to, and she would berate me for not knowing what I was tallking about - after all she had raised 3 kids no problems...
I now have little patience for those who don't respect the parents' wishes. Until you have been through NICU, no opinion, sorry.