% Sexuality
It is common, for cisgender people (people whose gender identity matches the one they were assigned at birth), especially parents after their kids come out (whether grown up or still children), to assume that being trans means you're gay, because they assume by default that someone is attracted to a member of the opposite sex.
This misconception can work in several ways, e.g.:
Generally speaking, it's never good to assume someone's sexuality. A trans person can be heterosexual, gay/lesbian or bisexual.
Brazen's Trans Women’s Safer Sex Guide http://librarypdf.catie.ca/PDF/ATI-20000s/26424.pdf
Booklet for trans women that focuses in the UK but is still relevant for everyone: http://www.tht.org.uk/~/media/4653aa766e3f4c1286fc515f17146f32.ashx
Sex education booklet for trans men that focuses in the UK but is still relevant for everyone
http://www.tht.org.uk/~/media/8F7D70D8C3B643109351E3D9A633529A.ashx
Sex education for gay trans men (trans men into into men) http://librarypdf.catie.ca/PDF/ATI-20000s/24654.pdf
FTM Sex Talk (Q&A about trans men)
If a cis man likes only women, he is heterosexual/straight. If he likes men, he's gay. If he likes men and women, he's bisexual.
If a trans man likes only women, he is heterosexual/straight. If he likes men, he's gay. If he likes men and women, he's bisexual.
If a cis woman likes only men, she is heterosexual/straight. If she likes women, she's gay. If she likes men and women, she's bisexual.
If a trans woman likes only men, she is heterosexual/straight. If she likes women, she's gay. If she likes men and women, she's bisexual.
There are other sexuality's, e.g. pansexual, demisexual, asexual, etc. Or aromantic/panromantic <insert sexuality here> here.
What about non-binary people? A non-binary person is someone who identifies as neither strictly male or female at a given moment, or who switches identities, etc. There are many different types of non-binary trans people!
It's generally wrong to put labels on anyone. A person is who they are, and they like who they like. Get over it!
One thing is certain: sexuality has nothing to do with gender identity. Gender identity is who you are, and sexuality is who you want.
Make sense now? Yes? Excellent!