I assume the poster is referring to this article which was published today. It doesn't confirm anything, just summarises what other outlets are reporting:
"The FBI declined to comment about reporting on Saturday including by conservative media outlets Fox News and the New York Post, citing law enforcement sources, that Robinson lived with a partner who was trans – a member of a community against whom Kirk rallied – and was cooperating with investigators.
Meanwhile, citing a half-dozen of its own sources familiar with the case, the left-leaning Axios said authorities were investigating whether Robinson believed Kirk’s views on gender identity were “‘hateful’ to people like Robinson’s transgender roommate”."