i can understand you being a little pissed at her, but at end of the day shes your sister and you need to support her IF she is preggo.
As for "killing" the guy, i was always told it takes "2 to tango" so hes not all to blame for this IF she is preggo, plus, seems you are quick enough to "kill" her guy or ex guy, whatever his status to her is at the moment, but willing to forgive the guy your married to who cheated on you and got his "bit" preggo while married to you....i know who id be "killing"
sorry if that sounds really nasty....but i just hate hearing how men always get branded the arsehole for getting a girl preggo, not sticking up for them in the slightest, cos there are some right fu**ers in the world, but she has loads of options to "stop" herself from falling preggo.
she might secretly be wanting a baby, but telling you it was an "accident". i know im scared to admit to people that im TTC, cos i know my family wont approve, but maybe she told him she was on the pill knowing well that she could fall preggo and he was none the wiser??
sorry im in a right rampage the night, nothing against you....sorry.
i would find out all the facts before you go around "shooting" people lol xx