Here is the NVC Process so you know what happens once your petition gets there. http://www.visajourney.com/wiki/index.php/NVC_Process
Its about 4 months at NVC.
Your Embassy is about a 3 to 4 month wait after Case Complete for an interview.
Why would it be suspicious a 25 and a 21 year old. You are adults. Long as you submitted evidence showing a bonafide marriage and ongoing relationship. You should have no issues and you have visited like you said.
