I'm dating a transsexual or transgendered girl. Would like advice or opinion.?

TS girls are by and large very attractive, even beautiful so I can understand your attraction. I think it is important for you both to meet and see whether the online fantasy survives physical reality. Who you date is your own business so for the interim until you are certain the relationship can work I would not mention to your family that she is TS. Why? Because that will entail a completely different emotional journey that you are yet to undertake - that is accepting you are gay/bisexual. At best you consider yourself bi-curious so it is a considerable jump to thinking about anal sex to actually having it and identifying yourself as gay. It will be a testing time for both of you. Take it slowly and good luck.