I’ve been in two step parent situations and I have bipolar.
Separating bipolar the illness and volatile blended relationships is imo essential in this crisis situation.Ill explain.
Firstly, his relationships with his children does not seem so relevant in this case, more your home environment and relationships.
When a powder keg occurs under the same roof whereby there are step children, particularly when the step parent and the step children have issues of an argumentive core the fact that bipolar moods “either high or low” frankly has little to do with the cause. To suggest so is purely speculative and if it is more likely to do with behaviours of the children or their mums need for advice she can obtain to get her children to respond better and take on more responsibility. Making his bipolar moods a possible major factor would be unfair on him.
In both cases I was a step parent, any inclusion of myself in issues including discipline, development of rules for the kids or even endorcing the mothers decisions was met with resentment from the kids. Inside the child’s mind runs the thought “you are not my dad” and “you are supporting my mum when she makes rules for me to follow”.
Unless the child was a toddler when the step dad came into their lives he is often seen as an intruder. This is why step parent situations often fail.
Im now of the view a step parent needs to be a nurturing kind of person that willingly encompasses his step children into his/her life as “mates” and best he/she does not get involved much at all in the upbringing of the children, is merely a person that offers encouragement in a calm manner. As he has bipolar his anger might flare quicker than some but is not the core problem.
In 12 months time I can’t see why things will change when the younger of the 2 is 18yo. The older child is 20yo and still lives at home so I guess the 18yo will also.
The real problem your man has is your children’s laziness and lack of responsibility which includes looking after animals. That factor is hindering his relationship with yourself and it is you alone that can do something about it. Teaching your kids that as they are adults, they are partially responsible for harmony in the home and your happiness.
You are in a tough situation. Tough love is your choice or risk not having a love life at all because the pressure any potential partner faces is obvious to most. You deserve love ,your kids need to acknowledge that and respond.