原文Their mother had nothing，and their father only seven thousand pounds in his own disposal，for the remaining moiety of his first wife's fortune was also secured to her child，and he had only a life interest in it.
主句 Their mother had nothing，并列句and their father only seven thousand pounds in his own disposal，（原因状语 for the remaining moiety of his first wife's fortune was also secured to her child，and he had only a life interest in it.）
把句子结构整理出来，你就一目了然了。
追问是后一句的意思。