If they are using some kind of newsgroups or torrent download program you will see some routers lock up which makes you lose connection for a few seconds then come back up. This happened to me all...
To me it sounds like either you're overloading the number of connections your router can maintain or the switch in the router is going bad, which would require a new router.
1589 Steam mobile Beta, I think
1589
twigg 2 Hours AgoSteam mobile Beta, I think