Hi there,
I second the KCCC as I use it on my daughter who has very fine tangly delicate 2c curls (the hardest type) KCCC makes her hair really curly, and helps with the frizziness, to shampoo I use Jessicurl HCC or Kinky Curly Come Clean for Conditioners I like Biolage Conditioning balm or KBB milk and for a leave in I use KCKT (I use with KCCC) KBB milk Or Biolage Conditioning balm (so I can use the same conditioners as leave ins!!) I would try the same products on both their hair and see how that goes, you may find something works better one one and vise versa but its really trial and error, going CG and cutting out silocones and sulphates has improved my little ones hair
Trying to work out my 5 year olds 2c fine frizzy/curly hair

Password; curlygirl

Loving KBB and Kinky Curly!!