There is a B vitamin called biotin that is well known for thickening hair and nails. You can find it in most drug stores where vitamins are sold and it costs about ten bucks. Here's more about biotin so you can read the facts for yourself. This was discovered in 1916 BTW.
Is there a law against leaving a 14 year old home alone with a 3 year old and a 1 year old for 6 and a half hours?
Nope as most places recognize 11 or 12 as the age of a sibling or babysitter to take care of kids this long so your answer here is no.