כ"ז בַּדֶּרֶךְ נָחַנִי ה' בֵּית אֲחֵי אֲדֹנִי
מ"ח לָקַחַת אֶת בַּת אֲחִי אֲדֹנִי לִבְנוֹ
The first one seems plural and the second is singular. However, there are two points that trouble me about the above observation:
1) I cannot understand why it would be plural. It doesn't really make much sense in context.
2) The תרגום of both is אחוהי which would seem to imply singular on both counts. When תרגום translates אֲחֵי that is clearly plural, such as במדבר כ"ז:ד, he actually leaves the word untouched and translates as אֲחֵי.
Is it possible that even אֲחֵי is singular here? (And if so, perhaps does not need to be corrected.) And of course, if so, the next question would be why does the word change?
Update 2016: Based on Anonymous's comment below (the second one) question #2 is not a question at all. In looking into it further, I came up with a theory to address my first question. The first פסוק is אליעזר's actual private prayer. אברהם sent him to find a girl from his family, seemingly without any further direction. So in truth, he could have ended up at any of אברהם's relatives and that would have sufficed. He was praising השם for guiding him to "the house of [one of] his master's brothers," אחי being used more loosely as a general reference to all relatives.
When telling over the story to רבקה's family, however, he felt that wouldn't make them feel terribly special. Using the singular form implied that he was specifically pleased with having found a girl from this particular family.