Game: Who am l?

I am your mother's brother's only brother in law. Who am I?

BONUS:

Alexander is stranded on an island covered in forest.

One day, when the wind is blowing from the west, lightning strikes the west end of the island and sets fire to the forest. The fire is very violent, burning everything in its path, and without intervention the fire will burn the whole island, killing the man in the process.

There are cliffs around the island, so he cannot jump off.

How can the Alexander survive the fire? (There are no buckets or any other means to put out the fire)

yep, goblet of fire.

The man can take a piece of wood, light fire into it and then light the end of the island while the other side burns, then the end will have burned out, and he can step there.

yep goblet of fire in Harry Potter 4#

What has a head a tail is brown but no legs

@Jatinsuman the riddle the more more take the more you leave behind. the awnser is footsteps

Can I say a riddle?
Actually 2.

@MyPeace you forgot the part that says :

now string them together and answer me this,
which creature would you be unwilling to kiss.

It was a sphinx that said it, wright?

Yep

This thing all things devours:
Birds, beasts, trees, flowers;
Gnaws iron, bites steel;
Grinds hard stones to meal;
Slays king, ruins town,
And beats high mountain down.