User blog:Monkey.D.Me/Garp Dragon Luffy Is that all??

Is Luffy the only son of Dragon?
'''I never thought about it until now that If Luffy can have a blood related brother or sister. Same question can be asked about Dragon, if he has any brother or sister. I had a really crazy theory that Shakky is daughter of Garp and since she became pirate, Garp chased her to capture her and bring her on the right track. Asusul Garp failed and let her be what she wanted to be. well thats my theory and you all know that my theories are crazy so feel free to comment on them and agree or disagree.'''

But to get back on the point 

'Is Luffy the only son of Dragon?'
Please comment your opinion and guesses

thanks