Unless your cousin lives with you in the same household to be considered personal use, you legally cannot share accounts. Don't ruin it for the rest of us, please.
Also, there is no limit to the number of redownloads, but please remember that you're not allowed to share your GOG account with other users as only you are entitled to download items from your account.
However, if you think about installing your game on a friend's machine or sharing it with others then please don't do it, okay? The same principle applies to movies - you're free to watch them anywhere you want, with anyone you want, as long as you don't share them with people who haven't purchased them.
https://support.gog.com/hc/en-us/articles/360001942753-FAQ-Downloads-and-streaming?product=galaxy
Your account and games are for your personal use only. If you want to share them, you can always buy a gift for that person. The DRM-free nature of our service means that we trust you that this will not be abused.
https://support.gog.com/hc/en-us/articles/212184489-Can-I-share-games-with-others-?product=galaxy
Re: Can GOG games be shared with others in my household?
In short, yes, you are.
https://www.gog.com/forum/general/can_gog_games_be_shared_with_others_in_my_household/post4