Though there are some exceptions, the age of consent is 17 in Texas. That means that an older person can lawfully engage in consensual sex with someone who is 17 years or older. Texas law explicitly forbids any person from engaging in sexual activity with a person under the age of 13.

Is it okay for a 16 year old to date a 12 year old?

Going on dates isnt per se illegal, but at your age, there are a large number of things that ARE illegal and could lead to him facing felony charges, even if hes only charged as a juvenile.

Is dating a 16 year old at 13 legal?

The question as phrased, the answer is no. It is not legal. If the 16 year old engages in any sexual conduct with the 13 year old, they could face statutory rape charges and the parental consent assuming there was any would have no bearing