Yes they can!
If one of your members also coaches in your club, that's totally fine! They will need seperate logins (one coach account and one member account). However, they can use the same email address to log in.
Once a password is already set up for their email address, the system will automatically use the same password for the second account. This should mean that when they log in, they should be able to select which account they'd like to log into.