New Baby and my twins boys will be 14 years apart !

Anybody else starting over ? I was young 19 with my twins now I'm gonna be 33 when baby arrives . I'm really worried how my kids will take the news that they are gonna have a baby brother or sis . I'm 5 weeks 3 days .

We don't know when to tell the boys either and how we should tell them . Any ideas. It's sad because they keep asking step dad and I for a dog . Now it's gonna be like surprise your not getting a dog but you can have a baby sis or brother .. yikes any advice?