Wanna see my friend naked (14 yrs)

Hi guys,I know this is gonna sound really weird, but I kinda wanna see my friend's penis. But before I ask how, I would like to do some explaining. After being with my best friend for about 3 years, I moved away to another country and we got separated. We have had some great times together. We would talk about girls together and stuff that normal teens would talk about. Although I think we're both straight, we have slept in the same bed together and went into the bath together (and yes, I saw his dick). After a year, I am finally going to meet him again and I am planning to have a sleep over with him. I know I wouldn't be able to convince him to go into the bath with me again, but I want to see his penis in any way. Any way to convince him?Thanks