My LO jus started walking independently (but still a bit wobbly) at 15+ months.. my mil said he is slow .. I mean , 15 months started walking independently really is considered slow ?

nope. my #3 walk at 15 months..now he is coming to 4 ...just like any kid. my #4 walk at 10 months...i am sure he wil like his peer later on in life even though he is a fast walker ! how soon they can walk isnt indication of their ability in later year