how to spawn two robots at a time

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this is my urdf file*

<?xml version="1.0"?>
<robot name="cougarbot">
    <link name="world"/>
    <link name="base_link">
        <visual>
            <geometry>
                <cylinder length="0.05" radius="0.1"/>
            </geometry>
            <material name="silver">
                <color rgba="0.75 0.75 0.75 1"/>
            </material>
            <origin rpy="0 0 0" xyz="0 0 0.025"/>
        </visual>
        <collision>
            <geometry>
                <cylinder length="0.05" radius="0.1"/>
            </geometry>
            <origin rpy="0 0 0" xyz="0 0 0.025"/>
        </collision>
        <inertial>
            <mass value="1.0"/>
            <origin rpy="0 0 0" xyz="0 0 0.025"/>
            <inertia ixx="0.0027" iyy="0.0027" izz="0.005" ixy="0" ixz="0" iyz="0"/>
        </inertial>
    </link>
    <joint name="fixed" type="fixed">
        <parent link="world"/>
        <child link="base_link"/>
    </joint>
    <link name="torso">
        <visual>
            <geometry>
                <cylinder length="0.5" radius="0.05"/>
            </geometry>
            <material name="silver">
                <color rgba="0.75 0.75 0.75 1"/>
            </material>
            <origin rpy="0 0 0" xyz="0 0 0.25"/>
        </visual>
        <collision>
            <geometry>
                <cylinder length="0.5" radius="0.05"/>
            </geometry>
            <origin rpy="0 0 0" xyz="0 0 0.25"/>
        </collision>
        <inertial>
            <mass value="1.0"/>
            <origin rpy="0 0 0" xyz="0 0 0.25"/>
            <inertia ixx="0.02146" iyy="0.02146" izz="0.00125" ixy="0" ixz="0" iyz="0"/>
        </inertial>
    </link>
    <joint name="hip" type="continuous">
        <axis xyz="0 0 1"/>
        <parent link="base_link"/>
        <child link="torso"/>
        <origin rpy="0 0 0" xyz="0.0 0.0 0.05"/>
    </joint>
    <link name="upper_arm">
        <visual>
            <geometry>
                <cylinder length="0.4" radius="0.05"/>
            </geometry>
            <material name="silver"/>
            <origin rpy="0 0 0" xyz="0 0 0.2"/>
        </visual>
        <collision>
            <geometry>
                <cylinder length="0.4" radius="0.05"/>
            </geometry>
            <origin rpy="0 0 0" xyz="0 0 0.2"/>
        </collision>
        <inertial>
            <mass value="1.0"/>
            <origin rpy="0 0 0" xyz="0 0 0.2"/>
            <inertia ixx="0.01396" iyy="0.01396" izz="0.00125" ixy="0" ixz="0" iyz="0"/>
        </inertial>
    </link>
    <joint name="shoulder" type="continuous">
        <axis xyz="0 1 0"/>
        <parent link="torso"/>
        <child link="upper_arm"/>
        <origin rpy="0 1.5708 0" xyz="0.0 -0.1 0.45"/>
    </joint>
    <link name="lower_arm">
        <visual>
            <geometry>
                <cylinder length="0.4" radius="0.05"/>
            </geometry>
            <material name="silver"/>
            <origin rpy="0 0 0" xyz="0 0 0.2"/>
        </visual>
        <collision>
            <geometry>
                <cylinder length="0.4" radius="0.05"/>
            </geometry>
            <origin rpy="0 0 0" xyz="0 0 0.2"/>
        </collision>
        <inertial>
            <mass value="1.0"/>
            <origin rpy="0 0 0" xyz="0 0 0.2"/>
            <inertia ixx="0.01396" iyy="0.01396 ...