When I was contemplating leaving t1, I saw both for a few weeks. T2 knew about T1, but T1 did not know about T2. I don't see an issue having more than one, though some Ts have issues with it. I wouldn't feel obligated to disclose.

Every once in a while I contemplate consulting with another T. Usually around what I can't talk to t2 about (transference and the like).