I've only seen
Tegan as tee-gan. I don't think it's dated, but I wouldn't expect it to be very popular for babies. It mostly makes me think of
Tegan Quin.
ETA: I'm in the US and we say Meg-an (rhymes with leg) and Tee-gan. I've never seen mee-gan or teg-an, but there might be people here with those pronunciations too. I've also seen
Kegan as both kee-gan and keg-an and
Regan as both reg-an and ree-gan.
This message was edited 5/29/2019, 2:26 PM