No problem with dating.
If you are asking about sex: " The Texas legal Age of Consent for sexual contact is 17 years old. nine states have a legal age of consent of 17. While there is no close-in-age exemption to the Texas legal age of consent, it is an acceptible defense in court if the defendant is less then 3 years older then the victim and the sexual act was consentual. There are no set close-in-age exemptions or "Romeo and Juliet laws" to Texas's age of consent. This means that anyone who engages in sexual activity with someone under the age of consent in Texas is liable for prosecution, including people only a few years older then their sexual partner and even two individuals who are both under the age of consent. The Age of Consent is the age at which a person is deemed by Texas law to be capable of consenting to, and engaging in, sexual acts. Anyone who engages in sexual activity of any type with a partner under the applicable Age of Consent is breaking the law and can be charged with crimes ranging from a misdemeanor to a felony (statutory rape) depending on the jurisdiction in which they are prosecuted. Texas's specific laws on the Age of Consent can be found above."
http://www.age-of-consent.info/states/Texas
Parents, of course, cannot give a minor permission to have sex because they would be assisting the minor in breaking the law.
The info on marriage is: "With Parental Consent - Male: 14; Female: 14; (consent must be given during 30 day period immediately preceding the date of application for license); Minimum Legal Age Without Parental Consent - Male: 18; Female: 18. Minors under 18 can petition court in his own name for permission to marry."
http://statelaws.findlaw.com/texas-l...ents-laws.html