No! That is a bizarre assumption. Family is family, and friends are friends. Friends come and go, but siblings/family are forever, whether you like it not :) . Social networking is wonderful but its very overrated too. Friends you make online are nothing like friends or family in real life. There is a delusion and fakeness with social networking and digital friends/friendships. People can lie and hide their true selves easily online, and oftentimes people online often feel a pressure to compete and compare themselves to their friends (which may turn into result in jealousy and animosity between friends) .
Humans are social but they are also physical too. Social networks help a lot but I feel nothing beats physical friends/friendships. Social networks are all about expanding and making connections (but is often by superficial means).
Siblings is a unique and different kind of bond and experience. You can make companion-ships regardless if you have siblings. I would even argue siblings are your first friends and teach you how to socialize and make friends and bond with others.