I suspect the family may have been split up after Henry died.
Not sure what happened to Isabella the mother
Robert was also admitted to the workhouse in October 1873 and then sent on to Forest Gate school/home. He's a lodger in 1881
Nicholas looks to have remained connected to Henry jnr, as they are together in 1891
I think you may be right the family was split up, at least for a while. For Nicholas and Henry jnr. staying connected, it appears Nicholas was 'reunited' with his sister Isabella after Henry jnr. died in 1904, as in the 1911 census he is part of her household (though stated as a lodger, rather than brother-in-law to Isabella's husband, while the late Henry's two children (Emily) Elizabeth and Ernest are correctly stated as niece and nephew).
Going back to the original question about Isabella's involvement with Robert Potts' estate and being sought after by her brother Henry in relation to it, you would think given that she was at least reunited with their brother Nicholas that it did get resolved. However, there is that Isabella Boyens of London who appears on F. H. Dougal & Co.'s 'Unclaimed Money Registry' in 1910 - suggesting it was still to be sorted 15 years on from the original newspaper entry in 1895. Obviously by 1910 (December 16 1895 onwards) she was Isabella Dickens, not Boyens, but there doesn't seem to be another Isabella Boyens this could have been.