Even if the user and host are the same, they can still be distinguished in the ~/.ssh/config.
Host gitlab.com
HostName git.company.com
User git
IdentityFile /home/whoever/.ssh/id_rsa.alice
IdentitiesOnly yes
Host kitlab.com
HostName git.company.com
User git
IdentityFile /home/whoever/.ssh/id_dsa.bob
IdentitiesOnly yes
Then you can use gitlab.com and kitlab.com instead of the hostname in your git remote.
git remote add g-origin git@gitlab.com:whatever.git
git remote add k-origin git@kitlab.com:whatever.git
You probably want to include the option IdentitiesOnly yes to prevent the use of default ids.
Ref: https://blog.developer.atlassian.com/different-ssh-keys-multiple-bitbucket-accounts/