One of the most poetic sections of Latvian and Eastern Slavonic songs is the cycle of songs containing orphan's complaints to her descendent mother (rarely to father) for her hard life with a stepmother. In these very popular songs in Latgale - complaints of orthodox (Eastern Slavonic) and catholic (mostly Latvian) orphans from Latgale are connected with the wedding ceremony of blessing before leaving to the church Such Latvian songs are notable by their distinct logic composition, amazing monotony of variants which appears also in songs' beginnings and descendent mother's replies. These replies usually come to 'three locks' that locked the descendent parent. The keys are - grass, yellow sand and a coffin board. In many songs the functions of each lock are listed as well as the attempts to remove those by orphan's appeal to the forces of nature. Such 'locks' of Eastern Slavonic are popular only among Belorussians of Latgale and adjoining regions of former Vitebsk province. In Russian songs, the images of locks may be borrowings from Belorussian. Here orthodox churches prevail as well as appeals of clergymen to a church bell with which an orphan tries to awake the descendent parents. The direct talk of an orphan with God does not exist in Russian songs, but is met mostly in Belorussian and Latvian songs, in which God and angels participate in the blessing. Along with songs containing the motive of three locks, both in Belorussian and Latvian-Latgalian the motive of an orphan meeting God, her appeal to God and to nature's forces with the appeal to dry the grass, break a coffin board, let her mother leave the heavens and the next world are still kept. In conclusion, in the songs of all three nations there are also many other motives which open the relations between an orphan, her descendent parents and an evil stepmother. All these are interesting also for the research of social and ethnic-psychological relations. We can express only suppositions concerning the origin of a song. Various linguistic and compositional features suggest the idea of Belorussian origin of the song in Latgale and in the centre. Using typically Latvian images of 'green grass' and 'yellow sands' in the song gives the idea of going back to the period of Baltic-Slavic unity. However, the theme of blessing an orphan before marriage is of much later origin in comparison with the epoch of Baltic-Slavic language unity. The third possibility is the appearance of songs in the environment of bilingual Eastern-Slavic Latvian bilingualism with the use of both Eastern-Slavic and Latvian song tradition.