It is narrated from Umm al-Ala' (may Allah be pleased with her) that her father took her to Sayyiduna Ali (may Allah be pleased with him), and Sayyiduna Ali (may Allah be pleased with him) allotted her a share while she was small. Sayyiduna Ali (may Allah be pleased with him) said: The child who eats food and bites on a crust is not more entitled to this stipend than the newborn who is still suckling.
All these reports indicate that he would allot a man a share in proportion to his own sustenance and that of his family, slaves, children and mount.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12977