Yes, same-sex marriage is allowed in Tibia! I've done it myself plenty of times.
You cannot be married if you are already married, but you may marry a character of the same sex.
Taken directly from the FAQ on Marriage: https://www.tibia.com/support/?subtopic=gethelp&entryid=79
Brighid Grand Explorateur - Applying to TibiaQA team as ModeratorNovember 19, 2024
Looking for new TibiaQA staff membersJuly 12, 2024
Interview with Solkrin - lead of the Customer Support team at CipSoftDecember 20, 2023