It is illegal to have. Part 95 requires GMRS radios to have pre-programmed frequencies (no keypad) and a non-removable antenna. No ham radio meets those requirements.
Since people are having trouble believing this, here are some relevant regulations:
CFR § 95.1761 GMRS transmitter certification.
(a) Each GMRS transmitter (a transmitter that operates or is intended to operate in the GMRS) must be certified in accordance with this subpart and part 2 of this chapter.
CFR § 95.1761 GMRS transmitter certification.
... No GMRS transmitter will be certified for use in the GMRS if it is equipped with the capabilities to operate in services that do not require equipment certification, such as the Amateur Radio Service....
It is completely legal to own a Baofeng UV-5R or purchase a GMRS version of it which has a keypad. It is completely legal to program GMRS/FRS frequencies into either radio and it is legal to broadcast on either one in case of emergency due to Part 95 Subpart E (c) (3) which states:
> Any individual who holds an individual license may allow anyone to operate his or her GMRS station if necessary to communicate an emergency message.
CFR § 95.1761 GMRS transmitter certification.
(a) Each GMRS transmitter (a transmitter that operates or is intended to operate in the GMRS) must be certified in accordance with this subpart and part 2 of this chapter.
CFR § 95.1761 GMRS transmitter certification.
... No GMRS transmitter will be certified for use in the GMRS if it is equipped with the capabilities to operate in services that do not require equipment certification, such as the Amateur Radio Service....
https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D...