Yes, it sounds like he has bonded with your husband. Trouble is your hubby can't make babies with your Sennie so double check he is not encouraging him by stroking him inappropriately - ie. on the back, tail, vent or under the wings. Try to keep petting to the head and neck only.
If your Sennie has been hand reared or is used to being an only bird he may not get on with another of his kind so this may not be the solution. If you do get another they will need separate cages. And be prepared for them not to get along at all. Another bird is very likely not going to be the answer to hormonal behaviour. He will still love your husband.
As Michael said, training will help. It will give him something to do. PLUS he will begin to pair the person training him with wonderful reinforcers! I.e. you become a person he looks forward to hanging out with! If you are going to train any bird, you need to find something they will work for. Does he have a favourite treat? Will he take that treat from you nicely? A treat is only one of many, many reinforcers. You can read about reinforcers here:
Reinforcement, Reinforcers, and how to identify and use them Reinforcement If the outcome to a behaviour is desirable, then we will repeat that behaviour. That outcome or consequence to the behaviour is therefore said to be reinforcing. Positive Reinforcement As trainers we can engineer the...
theparrotclub.co.uk
By all means buy a clicker, but it is the reinforcer that is the most important part of training. The clicker is a bridge or marker. It is a signal to tell the learner: "you did right - a reinforcer is coming!". You could just use the word, "Good!" instead. Once you have identified a workable reinforcer, then try target training. This is simply to get the bird to touch a target (usually the end of a chopstick) with a body part (usually a beak) for which he earns a reinforcer. This is the best video I've seen to teach you how to target:
As well as formal training, you can do other things to distract him for a while. Provide enrichment. Get him to forage. Change up his toys daily - it's a good idea to have a box of toys and rotate different ones in each day. Boxes can provide hours of entertainment, but depending on the individual bird, it can make them more hormonal. Access to boxes that they can climb into, drawers, cupboards, dark cubbyholes, space under chairs encourages more nesty behaviour. I know if I allow Kobe (Pionus) to these sort of spaces, he becomes more aggressive.