Testaments and heirs

[Tarbicus]

Does anyone know a good article/book on the relations between roman soldiers and their heirs?

This seems to have something on the subject:
Aspects of Friendship in the Graeco-Roman World (JRA Supplementary Series 43)

Cecilia Ricci concludes the set by discussing the 155 inscriptions by urban troops in Rome, almost all funerary, which mention friendship ...... Or was there simply a tendency for unmarried veterans to nominate those dearest to them, who were naturally their fellow-servicemen, as their beneficiaries?

Also in Journal of Roman Archaeology, supplement 34 - 'The Roman Army as a Community'. Here's a PDF of the intro:
eprints.bbk.ac.uk/archive/00000261/01/haynes2.pdf

Check out page 9.