Answer:
A tower at the root of all confusion.
The distance from the top of your head to the floor standing up straight.
I am your mother's brother's only brother in law. Who am I?
Which one of Santa's reindeer can be seen on Valentines day?
Sitting down you have it, Standing up you don't.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.