Hello Ghawi,

Thank you for posting in our community and for your provided sample.

After I investigated this matter further I determined that the reason for this behavior is in your columnLayouts definition. The third layout should be defined as an option to the second one however in your sample they are both defined as an options to the parent layout. I moved the third layout as an option of the second and your sample is working as expected:

        columnLayouts: [{
            key: "level1list",
            responseDataKey: "Data",
            autoGenerateColumns: false,
            primaryKey: "ID",
            columns: [{
                headerText: "ID",
                dataType: "number",
                key: "ID"
            }, {
                headerText: "fullname should be level 1",
                dataType: "text",
                key: "FullName"
            }],
            columnLayouts: [{
                key: "level2list",
                responseDataKey: "Data",
                autoGenerateColumns: false,
                autofitLastColumn: true,
                columns: [{
                    headerText: "full name should be level 2",
                    dataType: "text",
                    key: "FullName"
                }]
            }]
        }]

Your modified sample could be found at : http://jsfiddle.net/w4ehc9r4/1/

I believe you will find the following article from our documentation helpful:

Columns and Layouts(igHierarchicalGrid)

Please let me know if you need any further assistance with this matter.