var members = Umbraco.TypedContent(9999).Children("membersList")
		.Where(x => x.IsVisible()).OrderBy("order");
int chunkSize = 3;
var  memberGroups = members.Select((x, i) => new { Index = i, Value = x })
            .GroupBy(x => x.Index / chunkSize)
            .Select(x => x.Select(v => v.Value).ToList())
            .ToList();