Because Vasu is the BADI maa and Ambika is the CHHOTI maa. Alekh is badimaa's son and naveen is chhoti maa's son so avni being naveen's wife had to touch sadhna's feet.
hmmmm it still doesn't make sense to me
Even if they are son of choti maa... even if naveen was born before Alkeh no matter whose the mother he should still be considered older and no have avni touch sadi's feet. Thats just my take