(decedent was firefighter who died in line of duty and trial court determined that decedent's surviving "spouse" was not legal beneficiary of decedent's estate because "spouse" was born a male and, therefore, was not legally married to decedent under state law at time of decedent's death; surviving "spouse" had male genitalia and was diagnosed at age 18 with "gender dysphoria" and placed on feminizing hormone therapy and continued living as a female; surviving "spouse" change name to female name at age 21 and was issued amended birth certificate and obtained KS driver's license which was used to obtain TX driver's license which was then used to obtain TX marriage license at age 33; after wedding, surviving "spouse" underwent "genital reassignment" surgery which reassembled male genitalia into female; two years later, decedent died; decedent's mother and ex-wife sued seeking declaration that marriage was void; trial court granted summary judgment for mother and ex-wife; on appeal, court reversed on basis that genuine issue of material fact remained regarding surviving "spouse's" gender which requires expert testimony to resolve).