Nikaah & Marriage Issues

Marrying one's first cousin

Q: I'm really worried and need advice on the matter of first cousin marriages.

1. What is the Islamic view on the matter? Should I be worried about the research online which says the chances of having a kid born with some kind of disability increases with first cousin marriages.

2. Could you please give me famous examples, specifically of first cousin marriages in Islam. Did Nabi (sallallahu alaihi wasallam) marry his first cousin? Was Ali's (radhiyallahu anhu) marriage with Fatima his first cousin?

Abortion

Q: My gynecologist told my husband and I after the birth of our daughter that, if I should fall pregnant again me or the baby will die. My last born was a twin but I lost the one baby. There was complications with me in theatre because they could not control my bleeding and I could not have a baby for the past 7 months. Thats why I am asking if I can have an abortion if I fall pregnant again.

Husband lying about the value of the mahr jewellery

Q: I am in dire need of advice regarding dowry (mehr) in Islamic marriages. Jewellery of an x amount was given at the time of the nikkah as mehr. I have had doubts about the amount and when I asked my husband he refused to provide a slip, or say where it was purchased from. However upon investigation the findings are that the jewellery is worth 50 to 75% less than the price that was stipulated. Even the selling price would never have matched the price that was stipulated. What is the ruling on this? Is the nikaah still valid?