No, the line will be darker depending on the level of hcg, which usually depends on how far into the pregnancy you are. And sweetbee3's answers are very very wrong, identical twins are due to one fertilised egg splitting in to two, and non identical twins are due to the mother releasing two eggs which are then fertilised. Absolutely nothing to do with the sperm.
Please let me just correct some misunderstandings. I'm currently pregnant with identical twin girls, when we found out my gyney said that it's possible that I released 2 eggs as both babies were in different sacs, but though she was not sure I had to see a Professor who specialises in multiple pregnancies. Upon seeing this Professor he himself explained the whole conception of twins to hubby and me. The male has NOTHING to do with conceiving twins, only in determining sex. Even if he himself were a twin. The woman CAN in fact release 2 eggs at once or the egg can split into 2, which by the way happened to us and that's how identical twins happen.
And to answer your question, I don't believe a hpt can pick up if you're caring multiples, not even a bloodtest can. Congratulations on the pregnancy*
No. The darker the line, the stronger your hormones are. The hormone HCG that detects pregnancy. Has nothing to do with with, and when it comes to twins, it doesn't matter how many times in one day you had sex, only one sperm cell connects to the egg. The egg it's self then splits into two cells.
Hope this helps!!
The darkness of the line might have to more do with the concentratedness of the urine than anything else. The positive being 3 or 4 days before your expected period is a good sign, though.
Or the mother could release two eggs at once x