I think in my lifetime I have realized what Solomon is trying to tell us in theses two proverbs:

1. You will have many acquaintances in this life but few friends
2. Friendship will always be established or destroyed by tough times.

Friends are those whom have seen your best/worst sides, those who have suffered with you, that is the true friends Solomon refers too in fact they are those who he calls brothers/sisters. 

I am thankful I have had the opportunity to have some good brothers, sisters, real friends. 

P.S. If you have me as your friend you have found a brother in Christ.

A man of many companions may come to ruin, but there is a friend who sticks closer than a brother. Proverbs 18:24 ESV

A friend loves at all times, and a brother is born for adversity.
Proverbs 17:17 ESV