Aberewa hwe abofra ma ofifir se nna abofra so hwe aberewa ma nese tutu. (Akan)
Leqheku le thusa ngoana ha meno a hae a hlaha, ngoana o thusa leqheku ha meno a lona a oela. (Sesotho)
The old woman looks after the child to grow its teeth and the young one in turn looks after the old woman when she loses her teeth. (English)
This Ghanaian proverb appeared as proverb of the month on this site. The Sesotho translation is mine. I haven't been able to find an equivalent Sesotho proverb. You can also get quite a thorough "explanation" of the proverb on this page.