I feel sure that if this 'little' brother were to understand the process which triggers and strengthens his inclination, and then need to laugh, in the context you have referred too, he would find victory over his problem.
If this has been happening since he was a child then it is likely that he will have two 'things' he needs to know. The first is how it started. The second is how it is able to continue on.
When you are a child doing something which gets you into trouble, you initially view the problem without any lasting fear. However, after a few times of getting into trouble you may begin to worry about it. Little children cannot reasonably judge themselves. They need representation of their conduct through the eyes of their parents. Just so a child eventually finds it possible to question their own conduct in a meaningful way. What often goes wrong for a little child is personal to them in such a way, that right from the start they begin to have strong feelings about what they are doing. I mean parental anger disproportionate to the reality.
Physically this produces a release of chemicals in the brain, which make the child either fearful or proud. The fear is adrenaline coursing through the veins and giving rise to that 'sick in the stomach feeling'. Ordinarily if a child can control themselves they will quickly settle down emotionally and will even forget about it. If the fear seems too real, even in their bodies, then they will become angry and, in their childish way, fight back.
This young man needs to ask himself how he first reacted when this 'laughing' started. The Lord will help him to remember. Once he knows something of the answer he can begin to exercise his own will to 'think past' the outcome or consequence of laughing when he shouldn't, and focus instead on what's actually real to him at that moment. Is it something which is funny (he knows that it is not) or is he feeling physical stimulations which simply make him laugh. Another way to think about this can be:-
Anything which begins in small childhood can be deep rooted not just for possible spiritual reasons, but because fear or pride produce physically, emotional responses. After a few years the mind itself will 'learn' how to react, and the central nervous system will sympathetically produce all kinds of physical sensations in the body. These either make a young person angry or else they produce fear. Anger almost always leads to pride, and fear almost always leads to more fear.
These kind of feelings are not real feelings which are produced when we are told off for the first time. Little children always fear being told off until they learn how to either resist the telling off, or else shrink back from it. The feelings which I have described in the above paragraph are not real. They are not produced by a rebuke, but rather than by bodily sensations together with the thoughts which you described this young man as having and feelings when he laughs. Adrenaline is only released normally when we are confronted by a real threat. Such as the first time a small child is told off. They really do feel afraid. Whether that experience develops into anger or deeper fear and less self control, will almost certainly come from the way a parent deals with the issue. Anger will produce anger; and it may produce deep fear.
If this lad has a spiritual problem, which settled with him from his early childhood then that has to do with evil spirits. This possibility can only be discerned, it cannot be thought out. But what these two options have in common is the physical body and the mind. Spirit's can only really influence a person to the extent that the person themselves has consented. Fear is sufficient consent to an evil spirit. Fear initially has to do with the mind responding to a telling off, but it can quickly become a 'sympathetic' reaction which produces adrenaline; which in turn produces bodily reactions, and now we are afraid. Even as though we were really in trouble. Fear produces a physical response, but the physical response in the end produces greater fear. Its like saying 'it seems all the more real'. Evil spirit's make use of this condition of 'sin' and use it against us. But only if we allow them too. They cant force us to do something against our will. But they can make use of our fearfulness to effect our minds to believe we are in trouble, when we may not actually be in trouble.
Every man, both male and female, are subject to their bodies. It is called the 'body of sin' and it has recognizable traits. The mind, in a similar way is 'fleshy' and although this kind of sinning may not be physical, it still counts as though it were. Your young friend needs to ask himself the questions which will release him from his own physical responses. Laughing is physical; body and mind. If the issue really is a 'spiritual' one; needing deliverance, then how will the Lord not show him if he seeks the Lord's face. Learning or deliverance.
