Unfortunately, he cannot have a friend introduced to him at this point
Robos can live in pairs granted one very important detail, that they were raised together. However, even sibling and parent/offspring pairs never really end well and generally must be seperated or they wind up hurting one another fatally. You should never introduce two unfamiliar hamsters together as it will almost certainly result in the death of one or both of them. If he had a partner with him from birth until now, it would be a different story in that they could possibly live with one another, but because he doesn't, he unfortunately never can. Don't worry though, he won't be lonely! Hamsters are solitary by nature and only come together (in opposite sex pairs) for breeding purposes before heading on their way. Instead, try and offer him as much of your love as you possibly can
Best wishes