Rule 173 authorizes appointment of a guardian ad litem only when it appears that the next friend has an interest adverse to the person represented. See TEX. R. CIV. P. 173; Byrd v. Woodruff, 891 S.W.2d 689, 705 (Tex. App. - Dallas 1994, writ dism'd by agr.). If the court determines that a conflict exists, the court must appoint a guardian ad litem. See id. Also see: Miller v. Miller, 487 S.W.2d 382, 387 (Tex. Civ. App.-Fort Worth 1972, writ ref'd n.r.e.) (default judgment improper in divorce where no guardian ad litem appointed for mentally incompetent hospitalized wife); Gibson v. Blanton, 483 S.W.2d 372, 373-74 (Tex. Civ. App.-Houston [1st Dist.] 1972, no writ) (orig. proceeding) (court has discretion in determining whether to grant next friend's non-suit on behalf of minor or appointing guardian ad litem where there is a conflict between next friend and minor); Gallegos v. Clegg, 417 S.W.2d 347, 352-53 (Tex. Civ. App.-Corpus Christi 1967, writ ref'd n.r.e.) (guardian ad litem should be appointed where next friend disqualified to represent minor and injuries and prior history constitute adverse interest); Cooper v. Liverman, 406 S.W.2d 927, 931-32 (Tex. Civ. App.-Texarkana 1966, no writ) (guardian ad litem should be appointed where next friend's interest adverse to minor's in probate).