Your sister does have a point, you're assuming you can plan your life. Fate has a habit of only letting that happen in small doses. With regards to age, I understand you wanting kids, because that was all I ever wanted from a very young age but being a father at 46 honestly feels no different to being a father at 26 because I feel no different.
I hope you'll excuse me if I say you sound as if you have some slight self esteem issues. Why would no-one want you just because you are 40? Fourty is not old and you're a great person, funny, intelligent, articulate what more could a man want? Your options are open both now and for a long time in the future. You could have four children if you wanted and still not have the first for another 5 plus years. You're choices aren't running out, they are opening up.