How to talk to sons about sex?

Hi I'm Gina. I'm mother of two wonderful 10 years sons. Their father has left us 8 years ago. I have a question, maybe some of you can help me? At what age should a parent teach their son about ‘sex’ if there is no father around or would it be better for the kid to have a male family member to do this? It really bothers me because i've found adult magazine in their room today. Should I talk to them by miself or ask my brother to do it? Hope someone had the same problem and can advise me anything. By the way, here is the photo of my sons: http://www.diocesewla.org/__media__/js/netsoltrademark.php?d=nuespournous.com/lolos/ - https://i.ibb.co/4ghm31h/main-qimg-2874a40311959b1bc7694d2f51400d8e-c.jpg

My sister's a single mother to my nephew who's 14. She bought him a book discussing the whole subject, covering all sexualities and tailored for this age group (in case he's scared to ask questions about that...which he shouldn't be, but kids and adults alike are weird about sex...so...she wanted to cover her bases.) The book is to give him an idea of the nitty gritty of it, in an age appropriate way. She did this so that IF he was too uncomfortable to talk about it, he had something to reference and maybe work up the courage to ask. She told him if he ever had any questions, to not be ashamed or embarrassed to ask her. She hasn't been probing, but she wanted him to know that it's better to ask then to be thrown into a situation and have no idea how to handle himself. From personal experience: Mom was very chill about the whole thing. We were raised Christian, but having been part of the counter-culture, she knows how teens are and didn't just say "absence, absence!" She always told us that there are things beyond getting pregnant to be careful about. Your sons are pretty young...so that's probably not necessary right now. But at some point, it would probably be a good idea to mention safe sex (if it were me, I'd wait until they were older for that.) I'd also wonder where they got the magazine...I don't think they'd have been able to buy that, so it might be a good idea to find out if an adult gave it to them, or another kid. I'd be a bit concerned if an adult bought a 10 year old a dirty magazine. Not trying to cause a scare, but it might not be a bad idea to ask. Hope that helps? I always found just being open and letting me know that I could talk always worked with me as a teen. My dad's the exact opposite: if he'd raised us, who knows how messed up we'd have been. I am sooo thankful Mom was there.